The present invention relates to the field of aeroengines. The present invention relates more particularly to detecting deformation of fan blades, e.g. as a result of an airplane turbojet ingesting an object while in flight.
In flight, it is possible for foreign bodies or parts that have become separated from the turbojet to be ingested by the turbojet and to lead to damage inside it. It is also possible for manufacturing defects to lead over time to delamination of the blades. Above all, an object impacting against a fan blade runs the risk of damaging it.
For damage due to a turbojet ingesting foreign bodies (e.g. birds), the term used is foreign object damage (FOD). For damage due to the turbojet ingesting parts that have become separated (e.g. rivets, bolts, etc.), the term is domestic object damage (DOD). Ingesting foreign bodies (FOD) constitutes the main reason for flights being delayed or canceled, since as a general rule the impact is not perceived by the pilot during the flight and it is observed on the blade only while inspecting the airplane immediately before it takes off again.
Various known solutions exist for detecting the presence of FOD or of DOD. Those solutions seek to forecast when inspection and maintenance operations need to be performed in order to improve the operational availability of the airplane.
One known solution for detecting FOD is described in Document FR 2 937 079 in the name of the Applicant. That document relies on mounting accelerometers permanently on an engine and in recognizing the characteristic signature of an impact against the fan in the waveform of the time varying signals delivered by such accelerometers.